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My PC running on windows 10 was recently infected with a virus/trojan. I inserted a usb to it at some point , and connected it to my MacBook for clean formatting (I was using my MacBook to wipe it in hopes of getting rid of the virus).
I did not transfer any files from the usb to my MacBook, I have transferred a pdf file from my MacBook to the USB.
Under these circumstances, can my MacBook be infected with a virus this way?
As I understand your question:
You used a known thumb drive i.e. not an unknown device that looks like a thumb drive.
You may have infected a file on the thumb drive from an infected Windows Machine.
You plugged the thumb drive into your Mac and formatted the thumb drive.
You wrote a file to the freshly formatted drive from your Mac.
If I have interpreted correctly, then there is no mechanism I've ever heard of that could have infected your Mac.
Even with a more cavalier approach, cross platform malware is rare. Relax, you're good!
It would depend on the nature of the malware and the device, and what vulnerability it was targeting.
Without knowing any details, I would recommend you not trust the USB Thumb Drive.
FWIW, I would not recommend you trust any USB Thumb Drive you did not buy yourself or obtain from a trusted source (you are trusting them to have obtained it from a trusted source, ad infinitum).
It really depends on how the malware was written and what triggers it to execute. We can't be sure if the malware has the ability to infect the peripherals and external storage. If it does we can't be sure if the malware also runs on a Unix environment which is drastically different from Windows. But always it's better to be safe than sorry. Run a scan on your Mac if you can, and pay special attention to system abnormalities.
